Grand Canyon National Park will reduce the size of its bison herd through culling, trapping and moving the animals to other locations, the National Park Service said in a press release.

The bison were brought here in the early 1900s by a rancher who cross-bred them with cattle, then abandoned the project. The Arizona Game and Fish Department later took control of the herd and offered bison hunts in House Rock Valley, in the high desert of northern Arizona just east of the park border.

The herd, which once numbered around 100 animals, has since moved into the park, where it has grown. Estimates range from 400 to 600 animals. The animals are hard on vegetation, water sources and archaeological sites. Some fear the herd could grow to 800 animals in the next few years and as high as 1,200 to 1,500 in the next decade if nothing is done.

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The park has weighed various options to thin the herd, such as culling it with sharpshooters or trapping and moving the animals. The Arizona Game and Fish Department wanted to expand its buffalo hunt into the park.

The Park Service has rejected the hunting option. Instead, volunteers working with the park will selectively shoot animals. The meat will be distributed to the state, volunteers who participate, food banks and Indian tribes.